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/*
Jonathan Dummer
image helper functions
MIT license
*/
#include "image_helper.h"
#include <stdlib.h>
#include <math.h>
/* Upscaling the image uses simple bilinear interpolation */
int
up_scale_image
(
const unsigned char* const orig,
int width, int height, int channels,
unsigned char* resampled,
int resampled_width, int resampled_height
)
{
float dx, dy;
int x, y, c;
/* error(s) check */
if ( (width < 1) || (height < 1) ||
(resampled_width < 2) || (resampled_height < 2) ||
(channels < 1) ||
(NULL == orig) || (NULL == resampled) )
{
/* signify badness */
return 0;
}
/*
for each given pixel in the new map, find the exact location
from the original map which would contribute to this guy
*/
dx = (width - 1.0f) / (resampled_width - 1.0f);
dy = (height - 1.0f) / (resampled_height - 1.0f);
for ( y = 0; y < resampled_height; ++y )
{
/* find the base y index and fractional offset from that */
float sampley = y * dy;
int inty = (int)sampley;
/* if( inty < 0 ) { inty = 0; } else */
if( inty > height - 2 ) { inty = height - 2; }
sampley -= inty;
for ( x = 0; x < resampled_width; ++x )
{
float samplex = x * dx;
int intx = (int)samplex;
int base_index;
/* find the base x index and fractional offset from that */
/* if( intx < 0 ) { intx = 0; } else */
if( intx > width - 2 ) { intx = width - 2; }
samplex -= intx;
/* base index into the original image */
base_index = (inty * width + intx) * channels;
for ( c = 0; c < channels; ++c )
{
/* do the sampling */
float value = 0.5f;
value += orig[base_index]
*(1.0f-samplex)*(1.0f-sampley);
value += orig[base_index+channels]
*(samplex)*(1.0f-sampley);
value += orig[base_index+width*channels]
*(1.0f-samplex)*(sampley);
value += orig[base_index+width*channels+channels]
*(samplex)*(sampley);
/* move to the next channel */
++base_index;
/* save the new value */
resampled[y*resampled_width*channels+x*channels+c] =
(unsigned char)(value);
}
}
}
/* done */
return 1;
}
int
mipmap_image
(
const unsigned char* const orig,
int width, int height, int channels,
unsigned char* resampled,
int block_size_x, int block_size_y
)
{
int mip_width, mip_height;
int i, j, c;
/* error check */
if( (width < 1) || (height < 1) ||
(channels < 1) || (orig == NULL) ||
(resampled == NULL) ||
(block_size_x < 1) || (block_size_y < 1) )
{
/* nothing to do */
return 0;
}
mip_width = width / block_size_x;
mip_height = height / block_size_y;
if( mip_width < 1 )
{
mip_width = 1;
}
if( mip_height < 1 )
{
mip_height = 1;
}
for( j = 0; j < mip_height; ++j )
{
for( i = 0; i < mip_width; ++i )
{
for( c = 0; c < channels; ++c )
{
const int index = (j*block_size_y)*width*channels + (i*block_size_x)*channels + c;
int sum_value;
int u,v;
int u_block = block_size_x;
int v_block = block_size_y;
int block_area;
/* do a bit of checking so we don't over-run the boundaries
(necessary for non-square textures!) */
if( block_size_x * (i+1) > width )
{
u_block = width - i*block_size_y;
}
if( block_size_y * (j+1) > height )
{
v_block = height - j*block_size_y;
}
block_area = u_block*v_block;
/* for this pixel, see what the average
of all the values in the block are.
note: start the sum at the rounding value, not at 0 */
sum_value = block_area >> 1;
for( v = 0; v < v_block; ++v )
for( u = 0; u < u_block; ++u )
{
sum_value += orig[index + v*width*channels + u*channels];
}
resampled[j*mip_width*channels + i*channels + c] = sum_value / block_area;
}
}
}
return 1;
}
int
scale_image_RGB_to_NTSC_safe
(
unsigned char* orig,
int width, int height, int channels
)
{
const float scale_lo = 16.0f - 0.499f;
const float scale_hi = 235.0f + 0.499f;
int i, j;
int nc = channels;
unsigned char scale_LUT[256];
/* error check */
if( (width < 1) || (height < 1) ||
(channels < 1) || (orig == NULL) )
{
/* nothing to do */
return 0;
}
/* set up the scaling Look Up Table */
for( i = 0; i < 256; ++i )
{
scale_LUT[i] = (unsigned char)((scale_hi - scale_lo) * i / 255.0f + scale_lo);
}
/* for channels = 2 or 4, ignore the alpha component */
nc -= 1 - (channels & 1);
/* OK, go through the image and scale any non-alpha components */
for( i = 0; i < width*height*channels; i += channels )
{
for( j = 0; j < nc; ++j )
{
orig[i+j] = scale_LUT[orig[i+j]];
}
}
return 1;
}
unsigned char clamp_byte( int x ) { return ( (x) < 0 ? (0) : ( (x) > 255 ? 255 : (x) ) ); }
/*
This function takes the RGB components of the image
and converts them into YCoCg. 3 components will be
re-ordered to CoYCg (for optimum DXT1 compression),
while 4 components will be ordered CoCgAY (for DXT5
compression).
*/
int
convert_RGB_to_YCoCg
(
unsigned char* orig,
int width, int height, int channels
)
{
int i;
/* error check */
if( (width < 1) || (height < 1) ||
(channels < 3) || (channels > 4) ||
(orig == NULL) )
{
/* nothing to do */
return -1;
}
/* do the conversion */
if( channels == 3 )
{
for( i = 0; i < width*height*3; i += 3 )
{
int r = orig[i+0];
int g = (orig[i+1] + 1) >> 1;
int b = orig[i+2];
int tmp = (2 + r + b) >> 2;
/* Co */
orig[i+0] = clamp_byte( 128 + ((r - b + 1) >> 1) );
/* Y */
orig[i+1] = clamp_byte( g + tmp );
/* Cg */
orig[i+2] = clamp_byte( 128 + g - tmp );
}
} else
{
for( i = 0; i < width*height*4; i += 4 )
{
int r = orig[i+0];
int g = (orig[i+1] + 1) >> 1;
int b = orig[i+2];
unsigned char a = orig[i+3];
int tmp = (2 + r + b) >> 2;
/* Co */
orig[i+0] = clamp_byte( 128 + ((r - b + 1) >> 1) );
/* Cg */
orig[i+1] = clamp_byte( 128 + g - tmp );
/* Alpha */
orig[i+2] = a;
/* Y */
orig[i+3] = clamp_byte( g + tmp );
}
}
/* done */
return 0;
}
/*
This function takes the YCoCg components of the image
and converts them into RGB. See above.
*/
int
convert_YCoCg_to_RGB
(
unsigned char* orig,
int width, int height, int channels
)
{
int i;
/* error check */
if( (width < 1) || (height < 1) ||
(channels < 3) || (channels > 4) ||
(orig == NULL) )
{
/* nothing to do */
return -1;
}
/* do the conversion */
if( channels == 3 )
{
for( i = 0; i < width*height*3; i += 3 )
{
int co = orig[i+0] - 128;
int y = orig[i+1];
int cg = orig[i+2] - 128;
/* R */
orig[i+0] = clamp_byte( y + co - cg );
/* G */
orig[i+1] = clamp_byte( y + cg );
/* B */
orig[i+2] = clamp_byte( y - co - cg );
}
} else
{
for( i = 0; i < width*height*4; i += 4 )
{
int co = orig[i+0] - 128;
int cg = orig[i+1] - 128;
unsigned char a = orig[i+2];
int y = orig[i+3];
/* R */
orig[i+0] = clamp_byte( y + co - cg );
/* G */
orig[i+1] = clamp_byte( y + cg );
/* B */
orig[i+2] = clamp_byte( y - co - cg );
/* A */
orig[i+3] = a;
}
}
/* done */
return 0;
}
float
find_max_RGBE
(
unsigned char *image,
int width, int height
)
{
float max_val = 0.0f;
unsigned char *img = image;
int i, j;
for( i = width * height; i > 0; --i )
{
/* float scale = powf( 2.0f, img[3] - 128.0f ) / 255.0f; */
float scale = ldexp( 1.0f / 255.0f, (int)(img[3]) - 128 );
for( j = 0; j < 3; ++j )
{
if( img[j] * scale > max_val )
{
max_val = img[j] * scale;
}
}
/* next pixel */
img += 4;
}
return max_val;
}
int
RGBE_to_RGBdivA
(
unsigned char *image,
int width, int height,
int rescale_to_max
)
{
/* local variables */
int i, iv;
unsigned char *img = image;
float scale = 1.0f;
/* error check */
if( (!image) || (width < 1) || (height < 1) )
{
return 0;
}
/* convert (note: no negative numbers, but 0.0 is possible) */
if( rescale_to_max )
{
scale = 255.0f / find_max_RGBE( image, width, height );
}
for( i = width * height; i > 0; --i )
{
/* decode this pixel, and find the max */
float r,g,b,e, m;
/* e = scale * powf( 2.0f, img[3] - 128.0f ) / 255.0f; */
e = scale * ldexp( 1.0f / 255.0f, (int)(img[3]) - 128 );
r = e * img[0];
g = e * img[1];
b = e * img[2];
m = (r > g) ? r : g;
m = (b > m) ? b : m;
/* and encode it into RGBdivA */
iv = (m != 0.0f) ? (int)(255.0f / m) : 1.0f;
iv = (iv < 1) ? 1 : iv;
img[3] = (iv > 255) ? 255 : iv;
iv = (int)(img[3] * r + 0.5f);
img[0] = (iv > 255) ? 255 : iv;
iv = (int)(img[3] * g + 0.5f);
img[1] = (iv > 255) ? 255 : iv;
iv = (int)(img[3] * b + 0.5f);
img[2] = (iv > 255) ? 255 : iv;
/* and on to the next pixel */
img += 4;
}
return 1;
}
int
RGBE_to_RGBdivA2
(
unsigned char *image,
int width, int height,
int rescale_to_max
)
{
/* local variables */
int i, iv;
unsigned char *img = image;
float scale = 1.0f;
/* error check */
if( (!image) || (width < 1) || (height < 1) )
{
return 0;
}
/* convert (note: no negative numbers, but 0.0 is possible) */
if( rescale_to_max )
{
scale = 255.0f * 255.0f / find_max_RGBE( image, width, height );
}
for( i = width * height; i > 0; --i )
{
/* decode this pixel, and find the max */
float r,g,b,e, m;
/* e = scale * powf( 2.0f, img[3] - 128.0f ) / 255.0f; */
e = scale * ldexp( 1.0f / 255.0f, (int)(img[3]) - 128 );
r = e * img[0];
g = e * img[1];
b = e * img[2];
m = (r > g) ? r : g;
m = (b > m) ? b : m;
/* and encode it into RGBdivA */
iv = (m != 0.0f) ? (int)sqrtf( 255.0f * 255.0f / m ) : 1.0f;
iv = (iv < 1) ? 1 : iv;
img[3] = (iv > 255) ? 255 : iv;
iv = (int)(img[3] * img[3] * r / 255.0f + 0.5f);
img[0] = (iv > 255) ? 255 : iv;
iv = (int)(img[3] * img[3] * g / 255.0f + 0.5f);
img[1] = (iv > 255) ? 255 : iv;
iv = (int)(img[3] * img[3] * b / 255.0f + 0.5f);
img[2] = (iv > 255) ? 255 : iv;
/* and on to the next pixel */
img += 4;
}
return 1;
}